The ability to set a whipstock through tubing for milling a window for a lateral is a great time saver. The tubing doesn't need to be pulled and the resultant time saving translates into substantial cost savings. Various designs of through-tubing whipstocks have been developed, the earlier ones not being retrievable and the later ones incorporating a retrievable feature. U.S. Pat. No. 5,909,770 entitled Retrievable Whipstock uses a pair of pivoting links each connected to a common tension bar, which is pulled up relative to the whipstock body by a known setting tool. The set is held by wedges, which must be undermined to release the whipstock. The tension bar has wickers to dig into the casing below the tubing. In this tool, the best results were obtainable if the angle the pivoting links made with the longitudinal axis of the whipstock was less than about 60-70 degrees. The problem with the tool arose if it were to be used in different size casing. Even casing of the same size but different wall thickness could allow for link rotation in excess of the desired maximum. In response to this issue either adjustable length links were used which had to be correctly set for the anticipated casing condition at the anticipated whipstock location or spare links of the desired length had to be on hand and installed before running in the hole. This turned out to be inconvenient and somewhat imprecise. Accordingly one of the objectives of the present invention is to allow a single tool to set in a variety of internal diameters, with variations in excess of 1.5 inches. Additionally, a simply designed and reliable locking and release system is another objective of the present invention. Furthermore, a more reliable structure to facilitate retrieval while being maintained out of the way of the mill or mills is another objective of the present invention. To accomplish these objectives, some of the features of the present invention comprise specially shaped anchoring links, which anchor through edge wickers. The anchoring links are rotated into position by a tension rod system whose set position is secured with a simple and reliable locking ring system, which is selectively released. The upper end is hinged and biased to stay out of harms way during milling. These and other features of the present invention will become more readily apparent to one skilled in the art from a review of the detailed description of the preferred embodiment, which appears below.
Relevant whipstock patents include U.S. Pat. Nos.: 5,494,111; 5,195,591; 5,944,101; 5,860,474; 5,423,387; 6,167,961; Re 36,526; 5,796,167; 5,647,437; 5,595,247; 5,566,762; 5,467,819; 5,193,620; 5,647,436; 5,836,387. Also relevant are Baker Oil Tools Products H15050; H15076; H15043 and the TIW TTR Window Milling System and Weatherford Enterra's Thru-Tubing Window Milling System featuring the Pawl Locking System.